When it comes to coffee, we all know that Arabica is (mostly) better than Robusta. But dig a little bit deeper into Arabica, and you’ll find that there’s an entire world of different varieties out there. If you’ve ever seen the words “SL-28″, “Pacamara” or “Catuai” on a bag of coffee and had only a vague idea what they meant, this is for you.

Strictly speaking, varieties of coffee are separated into two distinct camps: varieties and cultivars. Varieties occur spontaneously through either freak mutation—for instance, growing much larger cherries than other plants of the same variety1—or through natural hybridisation with another variety (in rare cases a different species!). Cultivars are much the same, except that the changes are created or cultivated by humans.

The Anatomy and Morphology of the Coffee Plant poster, available from here.

In fact, Arabica itself is a relatively recent hybridisation of Robusta (Coffea canephora) and another, lesser known species of coffee called Coffea eugenioides2. In the area in Eastern Ethiopia where this happened, there are thousands of natural varieties of arabica growing in the wild!

One of the most knowledgeable coffee professionals in the world and a wonderful teacher, Peter Guiliano—director of the SCAA Coffee Symposium—recorded a video in 2012 that deals specifically with varieties. It is just under 30 minutes long, and represents a quick run-through of how Arabica made its way around the world, and how the different commercialised varieties and cultivars you would encounter today came about. It caps off with a very short description of the sorts of flavour profiles you can expect from some of them. It is well worth your time.

A legendary coffee variety that originated on the Boma Plateau, located in southeastern Sudan near to the Ethiopian border. This area belongs to a region considered to be the birthplace of the Arabica species. Sudan Rume has long been used by plant breeders as a source of “quality” genes, but is rarely planted because it doesn’t produce large yields.3

As prices of coffee go up, let’s hope more of these low-yield but delicious varieties are grown commercially. A while ago, Tim Wendelboe did a cultivar cupping at the Los Pirineos farm in El Salvador. Out of more than 50 cultivars, he rated Sudan Rume the highest.4

In this tutorial we will be building a low budget, computer controlled coffee roaster using a Popcorn Popper, an Arduino, and the Artisan RoasterScopesoftware. The github repo for this project is here. Follow along, and you’ll be enjoying delicious, freshly roasted coffee in no time!Continue reading “How to Make an Arduino Controlled Coffee Roaster”